Efforts on fabrication of quantum bits (qubits) have mostly been confined to university or government research labs, with little published on the mass production of qubit circuits. Therefore, many of the methods used to fabricate qubits in these laboratories utilize processes or equipment incapable of rapid, consistent fabrication. For example, most qubit fabrication methods utilize electron beam lithography (EBL). EBL is great for fabricating small feature sizes, but is usually very slow, taking several hours to write a wafer. The tradeoff then becomes using small samples with acceptable production time, or large samples with long production times. Some literature reports on rapid fabrication of superconducting phase qubits, but typically small samples are used that don't exploit the relative economies of scale that make volume semiconductor fabrication so attractive. Small samples can be utilized with quick turn-around time, but in the end many samples need to be fabricated. Therefore, the entire process flow needs to be repeated increasing the likelihood of errors at any step in the process flow.
Superconducting qubits based on Josephson junctions are one of the leading technologies proposed for quantum computing and cryptography applications that are expected to provide significant enhancements to national security applications where communication signal integrity or computing power are needed. However, presently these devices remain laboratory curiosities due to the difficulty in achieving reproducible results. Furthermore, the need for low temperature processing currently presents one of the more significant barriers to mass producing JJ superconducting qubits. The current thoughts are that low temperatures are required due to the delicate nature of the metal-oxide-metal JJs and that high temperature excursions diffuse the thin oxide that forms the tunnel junction, or induce a chemical reaction, thereby affecting both the junction energy barrier height and width. Therefore, to be able to reliably manufacture superconducting qubits and control diffusion caused by high temperatures would provide a revolutionary step towards making the ideas of quantum cryptography and computing a reality.